Explosion-proof panel board



Oct. 5, 1965 A. I. APPLETON EXPLOSION-PROOF PANEL BOARD 4 Sheets-Sheet 1 Filed Jan. 10 1961 \e INVENTOR Ara-mun [.APPLETQN Q .-W94%.,W,%J(QMM Oct. 5, 1965 A. 1. APPLETON 3,210,608

EXPLOSION-PROOF PANEL BOARD Filed Jan. 10, 1961 4 Sheets-Sheet 2 IN V EN TOR. ARTHUR I. APPLETON BY W 1, W at. am

Oct. 5, 1965 APPLETON EXPLOSION-PROOF PANEL BOARD Filed Jan. 10 1961 ATTYS.

w T & 0L mA m1 R U H T R A Ei/f /l/l/ 4? 27167 225 lll'll United States Fatent G 3,210,608 EXPLOSION-PROOF PANEL BOARD Arthur I. Appleton, Northbrook, Ill. (1713 Wellington Ave., Chicago 13, Ill.) Filed Jan. 10, 1961, Ser. No. 81,787 11 Claims. (Cl. 317-99) The present invention relates to explosion-proof fixtures for electrical systems and, more particularly, to explosion-proof panel boards for accommodating a plurality of circuit breakers and the associated wiring connecting them to the system.

Explosion-proof electrical fixtures are designed for use in areas where explosive or inflammable mixtures of gas or vapor are present in the surrounding atmosphere and likely to filter into the fixture. When this occurs, an are within the fixture due, for example, to operation of a circuit breaker or to an electrical breakdown, is likely to trigger an internal explosion. Fixtures such as explosion-proof panel boards must, accordingly, be capable of tolerating an internal explosion in such a manner that it is not permitted to trigger a further explosion in the surrounding atmosphere.

Heretofore, explosion-proof panel boards have been unwieldy and complex structure which are expensive to manufacture, particularly where a number of circuit breakers are involved. Moreover, where attempts have been made to facilitate installation and servicing of the circuit breakers, the complexity of the actuating linkage and sealing arrangement has correspondingly increased.

With the foregoing in mind, it is an object of the present invention to provide an explosion-proof panel board of relatively light, simple and compact construction yet capable of accommodating a substantially greater number of circuit breakers and their associated wiring than is possible in explosion-proof panel boards of the type heretofore known.

Another object is to provide an explosion-proof panel board of the character set forth and susceptible of housing a plurality of circuit breakers in a manner permitting them to be installed and replaced almost instantaneously.

Still another object is to provide an explosion-proof panel board of the foregoing type and including a simplified actuating arrangement for the circuit breakers and means for positively retaining them in place as an incident to closure of the panel board housing.

A further object is to provide an explosion-proof panel board of the character set forth including a circuit breaker housing having separate actuating and access panels and a mounting arrangement for the breaker housing providing a ready approach, with equal facility, to the actuating panel for operation and to the access panel for servicing.

Other objects and advantages will become apparent as the following description proceeds taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a front elevational view of a novel explosion-proof panel board exemplifying the present invention.

FIGS. 2 and 3 are front elevational views similar to FIG. 1 but with the breaker housing in two different positions.

FIG. 4 is an enlarged front elevational view of the explosion-proof panel board of FIG. 1 with certain parts broken away to show internal structure.

FIG. 5 is a further enlarged fragmentary side view detailing an arrangement for locking in operating position a breaker housing of the type illustrated in FIGS. 1 and 4.

FIG. 6 is an enlarged rear elevational view of the breaker housing portion of the panel board illustrated ice in FIG. 3 with circuit breakers removed to illustrate details of the breaker actuating linkage.

FIG. 7 is a further enlarged fragmentary vertical sectional view through a breather assembly and taken in the plane of the line'77 in FIG. 6.

FIG. 8 is a further enlarged fragmentary horizontal sectional view taken in the plane of the line 88 through the breaker housing of FIG. 6.

FIG. 9 is a side elevational view of the breaker housing of FIG. 6 with a portion shown in vertical section to illustrate the breaker mounting arrangement.

FIG. 10 is a front elevational view of another form of explosion-proof panel board also exemplifying the invention.

FIGS. 11, 12, 13 and 14 are further enlarged fragmentary vertical sectional views illustrating various forms of sealed swivel mounting connecting the breaker housing and terminal housing in explosion-proof panel boards embodying the invention.

FIG. 15 is a horizontal sectional view taken in the plane of the line 1515 through the swivel mounting illustrated in FIG. 11.

While the invention is susceptible of various modifications and alternative constructions, certain illustrative embodiments have been shown in the drawings and will be described below in considerable detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but, on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention as expressed in the appended claims.

Referring more specifically to FIGS. 1 to 9, inclusive, the invention is there exemplified in a novel explosionproof panel board 30 adapted to accommodate a plurality of circuit breakers. The panel board 30 comprises a breaker housing 31 which holds the individual circuit breakers, in this instance twelve in number, and a terminal housing 32 which holds a terminal block assembly 34 and the wiring associated with the breakers and the system in which they are used. The breaker and terminal housing 31, 32 are individually of explosion-proof construction, each being adapted to tolerate an internal explosion initiated by an electric are without triggering another explosion in the surrounding atmosphere. The breaker and terminal housings 31, 32 have interposed therebetween a sealed connector fitting 35 which carries electrical conductors but physically isolates the interior of each housing from the other, constituting an explosion-proof barrier therebetween.

The circuit breaker housing 31 (FIGS. 1 to 4 and 6 to 9) happens in this instance to be of substantially rectangular boxlike form. It defines a single compartment with a plurality of individual circuit breakers 36 stacked or nested closely together therein. One wall of the housing 31 has defined thereon a breaker actuating panel 38 having a corresponding plurality of levers 39 for switching and resetting the circuit breakers. The housing 31 also includes a novel arrangement for providing ready access to the circuit breakers 36 for installation or maintenance without disturbing the actuating panel 38.

The terminal housing 32 also happens in this case to be of generally rectangular boxlike form but is somewhat smaller in size than the breaker housing 31. The terminal housing 32 encloses the terminal block assembly 34 and has side walls which include integral hubs (not shown in detail) afi'ording ready connection with the conduits of the associated electrical system. Access to the terminal block assembly 34 in the housing 32 is readily provided by a relatively large circular access port 40 which is normally closed by means of a precisely fitting screw cover 41.

For the purpose of draining moisture which may accumulate within the housings 31, 32, and for releasing gaseous pressures due to an internal explosion while preventing the escape of hot gases or flame which might otherwise trigger an explosion in the surrounding atmosphere, each housing 'is provided with a pair of drain and breather fittings 42, 44. While such fittings may take a variety of forms, in the present instance they are of substantially identical construction and similar to the one disclosed in United States Patent No. 2,405,927, issued August 13, 1956, on the application of Nils A. Tornblom. Since the present invention is not particularly concerned with the details of the drain and breather fittings 42, 44, it will sufiice to note that each such fitting (FIG. 7) comprises a plug 45 threadedly secured to the housing with a sufficient number of threads to insure an explosionproof joint. The plug 45 has a smooth internal bore 46 which slidably receives a cylindrical stem 48 having a helical groove or the thread 49 on its outer periphery. The stem 48 fits relatively closely with the smooth wall of the bore to define a relatively long tortuous passage through which condensed moisture and gases may pass. The passage is of suflicient length to insure cooling of gaseous explosive products to a safe temperature before they reach the surrounding atmosphere. The stem 48 is held in position by a retainer washer 50 secured to its upper end as by means of a cap screw. The uppermost one of the fittings 42, 44 on each housing may also be provided with a shroud 51 (FIGS. 4 and 6) to prevent the entry of foreign matter into the interior of the box while permitting the venting of gaseous products in the manner previously described. This arrangement thus insures the safe dissipation of any pressures which may build up in either of the housings as a result of an internal explosion.

In accordance with one aspect of the invention, provision is made for detachably mounting a plurality of circuit breakers 36 with plug-in connections to the inner or reverse side of the actuating panel 38 via a breaker access port 52 in the housing wall opposite the actuating panel (FIGS. 2, 3, 6, 8 and 9). In furtherance of such objective, the actuating panel 38 has on its inner or reverse side a plurality of pairs of breaker mounting receptacles 54, 55, 56, each pair in this instance being adapted to hold two breakers 36. The latter are positioned by means of registration pins 57 on the receptacles and which enter into sliding engagement with recesses in the breaker casing. Each of the receptacles 54, 55, 56 is provided with sets of closely spaced resilient contact elements 58, 59 which slidably receive corresponding prong elements 60, 61 fixed to the circuit breaker. Connections between the terminals 58, 60 and their associated wiring may be made by means of terminal screws 62. Similarly, terminals 59, 61 may be connected to their associated wiring by means of terminal screws 64 (FIGS. 6 and 8).

To permit actuation and resetting of the breakers 36 from the outside face of the actuating panel 38 by levers 39, each of the latter has fixed thereto a threaded stem 65 which fits into a correspondingly threaded bore through the actuating panel, there being a sufficient number of threads on the stem and in the bore to maintain the explosion-proof integrityof the breaker housing. A resilient gasket 66 (FIG. 8), which may be outwardly convex in shape, is mounted on the stem 65 between the outer face of the actuating panel 38 and the lever 39. The thickness of the gasket 66 is such that it is placed under some compression when the lever 39 is in normal operating position and thus serves as a seal to prevent water or moisture from entering the breaker housing along the threaded stem 65. Rigidly fixed to the inner end of each stem 65 is an actuator arm 68 extending radially therefrom (FIGS. 6 and 8). Adjacent its projecting end, the arm 68 has a pivot pin 69 mounted thereon. The latter drivingly engages a slider bar 70 confined in one of the breaker receptacles. In this case, the bar 70 is formed with a rectangular opening 71 which receives the pin 69 of the actuator arm 68, and a second and somewhat larger rectangular opening 72 which receives toggle lever 74 of the breaker 36. To reduce wear, the material of the bar 70 may be outwardly flared as at 71A and 72A adjacent the respective openings 71, 72.

By reason of the foregoing arrangement, it will be perceived upon further reference to FIGS. 6 and 8 that rotation of the left-hand one of the levers 39 in a clockwise direction (when facing the actuating panel 38) will result in shifting of its associated slider bar 70 and breaker toggle lever 74 toward the right (as viewed from the actuating panel). By the same token, rotation of the same lever 39 in a counterclockwise direction will shift the slider bar and toggle lever 70, 74 in the opposite direction, or to the left.

As noted earlier herein, in the side opposite the actuating panel 38 the breaker housing is formed with one or more relatively large access ports 52 through which the breakers 36 may be inserted and removed. Each such access port is formed with internal threads 75 which receive a precisely fitted cover 76 adapted to define an explosionproof joint with the side wall of said breaker housing (FIGS. 6 and 8). Such joint preferably includes an annular shoulder 77 surrounding the port and which is tightly engaged by a flange on the cover and a gasket 77A.

For the purpose of maintaining the circuit breakers 36 in plugged-in position on the inner side of the actuating panel 38, each access cover 76 is provided with a pressure pad 78 adapted to bear against the breakers 36. The pad 78, which may be of resilient material such as sponge rubber, preferably has a sheet metal backing disk and is yieldably urged against the breakers 36 as by means of a resilient element 79. The element 79, in this instance a leaf spring, is pivotally attached to the central portion of the cover 76 as by means of a cap screw 80. The cover may, accordingly, be turned on the threads of the access port to open or close the same while the pressure pad remains fixed relative to the circuit breakers 36, thus applying a steady and uniform pressure tending to hold the breakers in place. The pressure pad 78 is large enough to insure an adequate bearing surface for engaging all the circuit breakers 36 opposite the cover but it may have a small central opening 81 for access to the cap screw 80.

In accordance with a further aspect of the invention, provision is made for mounting the circuit breaker housing in a manner affording a ready approach, with equal facility, to the actuating panel for operation and to the access panel for servicing. This is accomplished in the panel board 30 by making the circuit breaker housing 31 selectively movable relative to the terminal housing 32 while maintaining the explosion-proof integrity of both. In furtherance of such objective, the circuit breaker housing 31 is mounted upon a pair of axially alined swivel or trunnion members and may readily be swung between an operating position, wherein the actuating panel 38 is exposed as indicated in FIGS. 1 and 4, and a servicing position, wherein the access ports and covers 52, 76 are exposed as indicated in FIGS. 3 and 6 so that the breakers 36 may be serviced. The sealed connector fitting 35 is, accordingly, constructed to permit angular movement of the housings 31, 32 relative to each other while maintaining an explosion-proof joint carrying electrical conductors therebetween. Operatively associated with the sealed connector fitting 35, and axially aligned therewith, is a pivot plug 82 disposed for explosion-proof threaded engagement with a hub 84 at the lower end of the breaker housing (FIG. 4). The plug is bolted or otherwise rigidly fixed to a cantilever bracket 85 as by means of cap screws 86, the bracket being mounted on the wall or other adjacent support which carries the assembled panel board. The common axis of the sealed connector fitting and threaded plug is approximately parallel to the general plane of actuating panel 38 and the access ports 52 and their associated covers 76.

Provision is made for positively maintaining the breaker housing 31 in operating position and thus precluding unauthorized opening of the breaker access covers 76. This is effected by the use of a locking arrangement which may conveniently utilize a small conventional padlock 88 (FIGS. 4 and 5). The terminal housing may, accordingly, have a fixed depending lug 89 with a lower end of generally T-shaped cross section. The latter serves as a positive stop abutment for an upstanding bifurcated lug 90 fixed to the breaker housing as by means of cap screws 91. The bifurcated lug 90 is adapted to straddle central web 92 of the T-shaped portion of the depending lug 89, being yieldably retainable in that position as by means of a spring latch 94. The central web 92 of the lug 89 has a transverse bore 95 for receiving the shackle of the lock 88 which serves to positively retain the lugs 89, 90 in engagement (FIGS. 4 and 5). Referring more specifically to FIG. 11, the sealed connector fitting 35 in this instance may be formed of two telescoping sleeve members 96, 98, one being threaded into hub 99 of the terminal housing and the other being threaded into hub 100 of the breaker housing. The member 98 is formed with a relatively smooth cylindrical land 101 of somewhat greater diameter than its threaded portion. The land 101 is slidably but precisely fitted within a corresponding bore 102 in the member 96 with sulficient area overlapping to define an explosion-proof joint. The depending edge 104 of the member 96 may be inwardly flared to serve as a positive retainer for the land 101, the latter being axially and angularly movable relative to the bore 102. To insure maintenance of the ground continuity of the system, a grounding ring 105 of copper or other material having high conductivity is interposed between the members 96, 98. In the present case, the ring 105 is mounted in a peripheral groove in the land 101 in a position to make adequate electrical contact with the inner surface of the bore 102.

Supported between axially spaced shoulders 106, 108, inside the inner sleeve member 98 are a pair of spaced apart disks 109, 110 of appropriate insulating material (FIGS. 11 and 15). Each such disk is apertured to receive a plurality of electrical conductors 111. The conductors 111 are arranged with sufficient slack between the terminal block of the housing 32 and the terminal receptacles of the breaker housing 31 to permit the swivel motion of the terminal housing relative to the breaker housing without chafing or wire breakage. The space between the disks 109, 110 defines a sealing well which may be filled with any appropriate sealing compound 112 to define an explosion-proof barrier between the interior of the terminal housing and the interior of the breaker housing.

Turning now to FIG. 12, another embodiment of sealed connector fitting 35A is there shown mounted between the terminal and breaker housings 32, 31. The fitting 35A in this case comprises a first sleeve member 114 threaded into the hub 99 of the terminal housing, and a second sleeve member 115 threaded into the hub 100 of the breaker housing. The members 114, 115 have laterally enlarged end portions 116, 118 with precisely fitted abutting end surfaces held together by a coupling nut 119. The latter engages threads on the end portion 116 of the sleeve 114 and has a shoulder underlying the end portion 118 of the sleeve member 115. Ball bearings 120 may be interposed between the nut 119 and the end portion 118 to facilitate turning of the nut and to permit a substantially uniform application of sealing pressure between the abutting end surfaces of the members 114, 115. Electrical conductors 111 extend axially of the sealing fitting 35A and through a sealing well and barrier 112 in the member 114 similar to those described earlier herein. The fitting 35A is fixed relative to the breaker housing 31 as by means of a set screw 121 in the hub 100. Consequently, during swivel movement of the breaker housing 31, relative turning movement occurs 6 between the fitting 35A and the hub 99 of the terminal housing.

In FIG. 13 there is shown another embodiment of sealed connector fitting 35B situated between the terminal and breaker housings 32, 31. The fitting 35B comprises a sleeve member 122 threaded into the hub 99 of the terminal housing, and a sleeve member 124 threaded into the hub of the breaker housing. The members 122, 124 are sealingly connected as by means of a relatively heavy, flexible metallic conduit 125 integrally attached thereto. The conduit 125 includes one or more layers of resilient sealing material, such as rubber, and is susceptible of sufiicient torsional deformation to permit swivel movement of the breaker housing 31 for the purposes described earlier herein. The fitting 35B also includes longitudinally extending electrical conductors 111 which pass through a sealing well and barrier 122 in the sleeve member 124.

FIG. 14 shows a further embodiment of scaled connector fitting 35C comprising a single sleeve member 126 disposed in threaded engagement with the hubs 99, 100 of the terminal and breaker housings 32, 31. The fitting 126 may include a central enlargement 128 for engage ment by an appropriate turning tool. In this case, the fitting 35C is fixed relative to the breaker housing 31 and retained in place as by means of set screw 121 in hub 100. Consequently, upon swivel movement of the breaker housing 31, relative turning movement occurs between the member 126 and the hub 99 of the terminal housing 32. To facilitate maintenance of the explosion-proof integrity of the connection between these parts, a resilient O-ring 129 may be interposed therebetween and positioned by means of a peripheral groove in the member 126. The fitting 35C also includes longitudinally extending electrical conductors 111 and a sealing well and barrier 112 similar to those already described.

Turning now to FIG. 10, a modified explosion-proof panel board 130 also embodying the invention is there shown. The panel board 130 is adapted to handle a somewhat greater number of circuits and circuit breakers than the panel board 30 described earlier herein. Because many of the components of the panel board 130 are identical with those of the panel board 30, like reference numerals will be used to designate common parts or components.

The panel board 130 comprises a breaker housing 31 similar to the one previously described, a breaker housing 131 similar to the housing 31 but somewhat shorter in length, and a terminal housing 132 similar to the terminal housing 32 but double its width.

The terminal housing 132 includes two terminal block assemblies 34 and two access covers 41 and is actually equivalent to two of the housings 32 in tandem.

In this instance, the breaker housings 31 and 131 are susceptible of swivel mounting in the manner described above. They are connected at their upper ends to the terminal housing 132 by means of sealed connector fittings 35C such as illustrated in FIG. 14. Their lower ends are disposed in threaded explosion-proof engagement with fixed pivot plugs 82 each mounted on a cantilever support bracket 85 and having threads of the same hand and pitch as the fittings 35C. The breaker housings 31 may thus be turned between an operating position, illustrated by the position of the housing 131, and a servicing position, illustrated by the position of the housing 31 in FIG. 10. Both housings 31, 131 may be positively secured in operating position as by means of the latching and lock ing elements 89, 90, 94.

I claim as my invention:

1. On explosion-proof panel board for accommodating a plurality of circuit breakers, said panel board having a front face and comprising the combination of a terminal housing, a movable circuit breaker housing, a breaker actuating panel on said breaker housing, means for detachably mounting circuit breakers within said breaker housing on said actuating panel with plug-in connections, means defining a breaker access port in said breaker housing opposite said breaker actuating panel,

and an explosion-proof swivel connection between said terminal housing and said breaker housing whereby said breaker housing may be shifted between one position presenting said actuating panel to the front face of said panel board and an alternate position presenting said access port to the front face of said panel board.

2. An explosion-proof panel board for accommodating a plurality of circuit breakers, said panel board comprising, in combination, a terminal housing, a circuit breaker housing, a breaker actuating panel on said breaker housing, means for detachably mounting circuit breakers within said breaker housing on said actuating panel with plug-in connections, means defining a breaker access port in said breaker housing opposite said breaker actuating panel, a detachable cover fitted on said breaker access port in explosion-proof relation therewith, a first explosion-proof swivel connection between said terminal housing and said breaker housing, and a second explosionproof swivel connection between said breaker housing and a fixed support.

3. An explosion-proof panel board for accommodating a plurality of circuit breakers, said panel board comprising the combination of a fixed terminal housing, a circuit breaker housing, a plurality of circuit breakers, a breaker actuating panel on said breaker housing, means for detachably mounting said circuit breakers within said breaker housing on said actuating panel, means defining a breaker access port in said breaker housing opposite said breaker actuating panel, a detachable cover fitted on said breaker access port in explosion-proof relation therewith, a first explosion-proof swivel connection between said terminal housing and said breaker housing, a second explosion-proof swivel connection between said breaker housing and a fixed support, and means for releasably locking said breaker housing against movement relative to said terminal housing.

4. In an explosion-proof panel board, the combina tion comprising a terminal housing, a circuit breaker housing having an actuating panel and an access panel, a sealed connector fitting mounted in explosion-proof swivel engagement between said terminal housing and said breaker housing, a pivot member mounted between said breaker housing and a fixed support, said sealed connector fitting and pivot member being disposed in alignment and defining a common swivel axis in the general plane of said actuating panel and said access panel.

5. An explosion-proof panel board for accommodating a plurality of circuit breakers, said panel board having a front face and comprising, in combination, a circuit breaker housing defining a breaker compartment therein, a fixed support for said breaker housing, a plurality of circuit breakers, a breaker actuating panel on one side of said breaker housing, means detachably mounting said plurality of circuit breakers on the inner side of said actuating panel with plug-in electrical connections between each of said circuit breakers and said actuating panel with said circuit breakers disposed in said compartment, a breaker access panel on said housing disposed opposite said breaker actuating panel and having a breaker access port therein, a detachable cover fitted on said breaker access port in explosion-proof relation therewith, and means defining a swivel connection between said support and said breaker housing disposing the latter for angular movement between alternate positions presenting said actuating panel and said access panel alternately to the front face of said panel board.

6. In an explosion-proof panel board, the combination comprising a circuit breaker housing, a plurality of circuit breakers, a breaker actuating panel on said housing, means for detachably mounting said circuit breakers within said housing on said actuating panel with plug-in connections, means defining a breaker access port in said housing opposite said breaker actuating panel, a detachable cover fitted on said access port in explosion-proof relation therewith, and a pressure pad interposed between said circuit breakers and said cover, said pressure pad having a face area which is urged into contact with said circuit breakers when said cover is fitted on said access port and being adapted to retain the same in engagement with said plugin connections.

7. In an explosion-proof panel board, the combination of a circuit breaker housing, a plurality of circuit breakers, a breaker actuating panel on said housing, means for detachably mounting said circuit breakers within said housing on said actuating panel with plug-in connections, a breaker access panel on said housing opposite said breaker actuating panel and having a breaker access port therein, a detachable cover fitted on said access port in explosionproof relation therewith, and a resiliently loaded pressure pad interposed between said circuit breakers and said cover, said pressure pad having a face area in contact with said circuit breakers.

8. In an explosion-proof panel board, the combination comprising a circuit breaker housing, a plurality of circuit breakers, a breaker actuating panel on said housing, means for detachably mounting said circuit breakers within said housing on said actuating panel with plug-in connections, a breaker access panel on said housing opposite said breaker actuating panel and having a breaker access port therein, a detachable cover fitted on said access port in explosion-proof relation therewith, a pressure pad interposed between said circuit breakers and said cover and having a face area in contact with said circuit breakers, means for resiliently loading said pressure pad when said cover is fitted in said access port, and a swivel connection between said pressure pad and said detachable cover.

9. A multiple circuit breaker explosion-proof panel board comprising, in combination, a fixed terminal housing, a movable circuit breaker housing, a plurality of circuit breakers stacked within said breaker housing, a breaker actuating panel on said housing, means for detachably mounting said circuit breakers on said actuating panel with individual plug-in connections, means defining an access port in said breaker housing opposite said actuating panel and having an area exposing said stacked circuit breakers, a detachable cover fitted on said access port in explosion-proof relation therewith, and means defining a rotatable explosion-proof electro-mechanical connection between said terminal housing and said breaker housing rendering the latter shiftable between an operating position and a maintenance position relative to said terminal housing.

10. An explosion-proof panel board for accommodating a plurality of circuit breakers and comprising, in combination, a terminal housing, a circuit breaker housing, a breaker actuating panel on said breaker housing, means for detachably mounting circuit breakers within said breaker housing on said actuating panel with plug-in connections, means defining a breaker access port in said breaker housing opposite said breaker actuating panel, and an explosion-proof electro-mechanical swivel connection between said terminal housing and said breaker housing whereby the latter may be shifted relative to said terminal housing between alternate positions substantially degrees apart.

11. An explosion-proof panel board as set forth in claim 2, and having a plurality of breaker mounting receptacles on the inner side of said breaker actuating panel, a plurality of circuit breakers on said mounting receptacles including toggle levers for operating the same, and having plug-in terminal elements thereon, a plurality of plug-in terminal elements on said receptacles adapted to receive said elements of said breakers, a plurality of slider bars on said receptacles each engageable with the toggle lever of a circuit breaker, a plurality of breaker actuating levers on the outer side of said actuating panel, a plurality of stems connected to respective ones of said actuating levers and mounted in explosion-proof relation with said actuating panel, and means for mechanically connecting respective ones of said stems and said slider bars for setting and resetting the circuit breakers associated therewith.

References Cited by the Examiner UNITED STATES PATENTS '10 Bush 317-1l9 Hellmann 317-120 X Robbins 317-420 Bingenheimer 200-172 Locher 317-99 X Appleton 17486 Casey 3l7119 Piteo 200172 10 KATHLEEN H. CLAFFY, Primary Examiner.

SAMUEL BERNSTEIN, E. JAMES SAX, JOHN F.

BURNS, Examiners. 

1. ON EXPLOSION-PROOF PANEL BOARD FOR ACCOMMODATING A PLURALITY OF CIRCUIT BREAKERS, SAID PANEL BOARD HAVING A FRONT FACE AND COMPRISING THE COMBINATION OF A TERMINAL HOUSING, A MOVABLE CIRCUIT BREAKER HOUSING, A BREAKER ACTUATING PANEL ON SAID BREAK HOUSING, MEANS FOR DETACHABLY MOUNTING CIRCUIT BREAKERS WITHIN SAID BREAKER HOUSING ON SAID ACTUATING PANEL WITH PLUG-IN CONNECTIONS, MEANS DEFINING A BREAKER ACCESS PORT IN SAID BREAKER HOUSING OPPOSITE SAID BREAKER ACTUATING PANEL, AND AN EXPLOSION-PROOF SWIVEL CONNECTION BETWEEN SAID TERMINAL HOUSING AND SAID BREAKER HOUSING WHEREBY SAID BREAKER HOUSING MAY BE SHIFTED BETWEEN ONE POSITION 